gpiolib: Make it possible to exclude GPIOs from IRQ domain

When using GPIO irqchip helpers to setup irqchip for a gpiolib based
driver, it is not possible to select which GPIOs to add to the IRQ domain.
Instead it just adds all GPIOs which is not always desired. For example
there might be GPIOs that for some reason cannot generated normal
interrupts at all.

To support this we add a flag irq_need_valid_mask to struct gpio_chip. When
this flag is set the core allocates irq_valid_mask that holds one bit for
each GPIO the chip has. By default all bits are set but drivers can
manipulate this using set_bit() and clear_bit() accordingly.

Then when gpiochip_irqchip_add() is called, this mask is checked and all
GPIOs with bit is set are added to the IRQ domain created for the GPIO
chip.

Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt
index 6cb35a78eff4..368d5a294d89 100644
--- a/Documentation/gpio/driver.txt
+++ b/Documentation/gpio/driver.txt
@@ -262,6 +262,12 @@ symbol:
   to the container using container_of().
   (See Documentation/driver-model/design-patterns.txt)
 
+  If there is a need to exclude certain GPIOs from the IRQ domain, one can
+  set .irq_need_valid_mask of the gpiochip before gpiochip_add_data() is
+  called. This allocates .irq_valid_mask with as many bits set as there are
+  GPIOs in the chip. Drivers can exclude GPIOs by clearing bits from this
+  mask. The mask must be filled in before gpiochip_irqchip_add() is called.
+
 * gpiochip_set_chained_irqchip(): sets up a chained irq handler for a
   gpio_chip from a parent IRQ and passes the struct gpio_chip* as handler
   data. (Notice handler data, since the irqchip data is likely used by the